This invention relates to a computer system having a plurality of storage systems, and more particularly, to a management method for data requested for data write in a thin provisioning volume.
Storage systems provide logical volumes (LUs) to host computers by statically assigning storage areas of disk drives. However, the LUs have the following problems.
For example, there is a problem in that a storage capacity of the disk drives assigned to the LUs becomes larger than a storage capacity to be actually used by the host computer, which is called over provisioning. This is because the storage capacity to be used by the host computer cannot be grasped with accuracy. Another problem resides in that operation costs required for changing LU capacities are high.
As a technique for solving the problems described above, there is known a technique called thin provisioning. The storage systems provide volumes realized by the thin provisioning (thin provisioning volume: TPLU) to the host computers. Thus, the host computers recognize the TPLUs provided by the storage systems as volumes having a storage capacity larger than that of the disk drives actually assigned to the respective TPLUs.
Upon reception of a write request to a TPLU from the host computer, the storage system dynamically assigns an unwritten storage area of a storage pool to the TPLU requested for data write.
In addition, JP 2007-102455 A discloses a technique of setting a storage pool including an LU of a storage system itself (internal LU) and an LU provided by an external storage system (external LU).
According to the technique disclosed in JP 2007-102455 A, the storage system can set a single storage pool including both the internal LU and the external LU. However, there has been a problem in that an administrator has to transfer data in units of TPLUs when a storage pool capacity becomes short, that is, capacity scalability of the storage system that provides the TPLU is low.